ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-6-1373-2006The heterogeneous chemical kinetics of N<sub>2</sub>O<sub>5</sub> on CaCO<sub>3</sub> and other atmospheric mineral dust surrogatesKaragulianF.1SantschiC.RossiM. J.1Ecole Polytechnique Fédérale de Lausanne(EPFL), Laboratoire de Pollution Atmosphérique et Sol (LPAS), Bâtiment CH H5, Station 6, CH-1015 Lausanne, Switzerland020520066513731388This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This article is available from http://www.atmos-chem-phys.net/6/1373/2006/acp-6-1373-2006.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/1373/2006/acp-6-1373-2006.pdf

Uptake experiments of N<sub>2</sub>O<sub>5</sub> on several mineral dust powder samples
were carried out under continuous molecular flow conditions at 298&plusmn;2 K.
At [N<sub>2</sub>O<sub>5</sub>]<sub>0</sub>=(4.0&plusmn;1.0)&times;10<sup>11</sup> cm<sup>&minus;3</sup> we
have found &gamma;<sub>ss</sub> values ranging from (3.5&plusmn;1.1)&times;10<sup>&minus;2</sup>
for CaCO<sub>3</sub> to (0.20&plusmn;0.05) for Saharan Dust with &gamma;<sub>ss</sub>
decreasing as [N<sub>2</sub>O<sub>5</sub>]<sub>0</sub> increased. The uptake coefficients
reported in this work are to be regarded as upper limiting values owing to
the fact that they are based on the geometric (projected) surface area of
the mineral dust sample. We have observed delayed production of HNO<sub>3</sub>
upon uptake of N<sub>2</sub>O<sub>5</sub> for every investigated sample owing to
hydrolysis of N<sub>2</sub>O<sub>5</sub> with surface-adsorbed H<sub>2</sub>O. Arizona Test
Dust and Kaolinite turned out to be the samples that generated the largest
amount of gas phase HNO<sub>3</sub> with respect to N<sub>2</sub>O<sub>5</sub> taken up. In
contrast, the yield of HNO<sub>3</sub> for Saharan Dust and CaCO<sub>3</sub> is lower.
On CaCO<sub>3</sub> the disappearance of N<sub>2</sub>O<sub>5</sub> was also accompanied by
the formation of CO<sub>2</sub>. For CaCO<sub>3</sub> sample masses ranging from 0.33 to
2.0 g, the yield of CO<sub>2</sub> was approximately 42&ndash;50% with respect to the total number of N<sub>2</sub>O<sub>5</sub> molecules taken up. The reaction of
N<sub>2</sub>O<sub>5</sub> with mineral dust and the subsequent production of gas phase
HNO<sub>3</sub> lead to a decrease in [NO<sub>x</sub>] which may have a significant
effect on global ozone.